1. Field of the Invention
The present invention relates to an optical disk drive, and more particularly, to a protection device for protecting a flat cable which is connected between a tray and a main board.
2. Description of the Prior Art
An optical disk drive utilizes a flat cable electrically connected to a movable tray and a fixed main board for providing transmission of electricity and signals of electrical components of the tray. The reliability of the optical disk drive could be maintained with stable transmission of electricity and signals in a long period of operation when the flat cable moves with the tray smoothly.
As shown in FIG. 1, FIG. 1 is a section diagram of a conventional optical disk drive 10 disclosed in TW patent 568326. The optical disk drive 10 includes a hollow casing 11, whereon a main board 12 and a tray 13 are disposed. The main board 12 is fixed inside the casing 11. The flat cable 14 includes a fixing portion 14a and a movable portion 14b. An end of the fixing portion 14a which is set on a casing 11 is connected to the main board 12, and an end of the movable portion 14b is connected to a circuit board 15 disposed on a bottom of the tray 13 for providing the transmission of electricity and signals of the electrical components of the tray 13, such as a spindle motor 16 and a pickup head 17. The tray 13 is drawn out of the casing 11 for replacing an optical disk 18 and is slid in the casing 11 for reading data on the optical disk 18. The spindle motor 16 rotates the optical disk 18, the pickup head 17 moves along radial direction of the optical disk 18 for reading data on the optical disk 18, and then the data on the optical disk 18 is transmitted to the main board 12 for processing via the circuit board 15 and the flat cable 14.
Because the tray 13 have to be drawn out of the casing 11 for replacing the optical disk 18 easily, the movable portion 14b of the flat cable 14 made of thin and soft plastic materials is easily dropping. The over dropping movable portion 14b, as shown a dotted circle in FIG. 1, often touches or engages with an edge of the casing 11 easily, so that the flat cable 14 is damaged when the tray 13 slides in the casing 11. The flat cable 14 is even short to affect the transmission of electricity and signals or hinders the tray 13 from sliding in/out the casing 11. In order to solve above-mentioned problems, a dropping part of the movable portion 14b can be coated with Mylar to form a supporting portion 14c in the prior art, so that elasticity of the flat cable 14 is improved for holding the movable portion 14b and for preventing the movable portion 14b from dropping.
However, the elasticity of the flat cable 14 is not strong originally. After adding a weight of the supporting portion 14c on the flat cable 14, the flat cable 14 drops down more easily, especially in a surrounding at high temperature with frequent operation. Besides, when the tray 13 slides in the casing 11, friction between the movable portion 14b and casing 11 hinders the movable portion 14b from moving backwards, so that the movable portion 14b drops down easily. Therefore, a protection device for protecting the flat cable in the conventional optical disk drive still has some problems which have to be solved.